J. E. Annis in his U.S. Pat. No. 3,500,062 issued Mar. 10, 1970 and entitled DIGITAL LOGIC APPARATUS, included herein by reference, describes complementary-symmetry metal-oxide-semiconductor (COS/MOS or, more simply, CMOS) exclusive-OR and exclusive NOR gates. In these circuits a first of two logic input signals is applied to a simple CMOS push-pull pair logic inverter to obtain its logical complement. This first logic input signal and its complement are then used to selectively enable either a transmission gate or a CMOS push-pull pair logic inverter. When the transmission gate is enabled, it passes the second logic input signal without inversion to the logic output of the gate. When the logic inverter is enabled, it provides inverted response to the second logic input signal at the logic output of the gate.
Recently, field effect transistors have been developed which have electrically alterable threshold voltages, or V.sub.T s, which can be programmed by applying voltages between the gate and one of the other electrodes of the device, which voltages exceed those used as normal logic or signal levels. Thereafter, non-volatile memory in these FETs retains the programmed threshold voltage. The present inventor in his U.S. patent application Ser. No. 213,361, filed Dec. 5, 1980 and entitled PROGRAMMABLE LOGIC GATES AND NETWORKS, abandoned in favor of a like-titled application filed Mar. 20, 1983, patented Jan. 22, 1985 as U.S. Pat. No. 4,495,427, and incorporated herein by reference, describes programming the threshold voltages of such devices for conditioning them to be strongly enhancement-mode or strongly depletion-mode in their characteristics, thereby to function as either open- or short-circuits to programmably interconnect CMOS field effect transistors into logic gates or networks of logic gates. The programming of the threshold of these devices is carried on by application of programming voltages via the same input terminals used for normal logic inputs. This use of two different regimes of signal for different purposes, but applying them through the same terminals, is referred to as "reflex" operation.